According to rapid international industrialization and the development of technology, the usage of the earth's resources, such as oil, has increased. Thus, from a global viewpoint, the stable production and supply of oil has arisen as a very important issue.
For this reason, interest in the development of small marginal oil fields or deep-sea oil fields, which have been disregarded because of their low potential profitability, has increased. Therefore, with the development of offshore drilling techniques, drill ships having drilling equipment suitable for development of such undersea oil fields have been proposed and developed.
In a conventional oil drilling technique, a rig ship or a fixed type platform, which can be moved only by tugboats and is anchored at a position on the sea using mooring apparatuses to conduct an oil drilling operation, has been mainly used.
However, recently, drill ships, which are provided with advanced drilling equipment and have structures similar to typical ships such that they are able to make voyages under their own power, have been developed and used for undersea oil drilling.
To develop small marginal fields, the drill ship is constructed such that it can move under its own power without using tugboats, in consideration of working conditions in which the drill ship must frequently change its stationary position. Therefore, in the drill ship, which is designed such that it can move under its own power, superior traveling performance must be regarded as an important point of the drill ship.
Meanwhile, a moon pool, which is relatively large, and through which drilling pipes are moved to the bottom of the sea, is formed through the drill ship in a central portion thereof. The moon pool is indispensable for the function of the drill ship but becomes a weak point in view of the anchoring of the ship, the voyage stability and the voyage performance of the ship.
Particularly, in a conventional drill ship, due to a sloshing phenomenon, which is induced by relative movement between seawater in the moon pool and seawater outside the ship, when the drill ship runs, resistance is increased, the velocity thereof is reduced, power consumption is increased, fuel consumption is increased, and the ship hull is damaged.
Furthermore, in the case of the conventional drill ship, seawater may overflow onto the ship due to the motion of seawater in the moon pool, with the result that the safety and work efficiency of workers are reduced.